1. Field of the Invention
This invention relates to an insert rotary cutter having a plurality of indexable cutter inserts attached thereto through respective support members.
2. Prior Art
One conventional insert rotary cutter for processing a surface of a metal workpiece includes a cutter body having a plurality of pockets formed in one end in circumferentially distributed relation and a plurality of indexable cutter inserts attached respectively to the pockets through support members of hard wear resistant metal interposed therebetween. It is appreciated that the insert rotary cutter of this type possesses such advantages that the cutter body is not subject to wear or abrasion, and that, even if the cutter inserts suffer from damage, the support members prevent the cutter body from being damaged and at most an exchange of the inserts and the support members is simply required to restore the damaged cutter. Since the support members have complicated shapes and are to be manufactured with high precision, precision cast steel hardened by heat treatment is conventionally utilized to manufacture them. In addition, the conventional support members include recesses to respectively accommodate the inserts, each recess having a depth generally equivalent to the thickness of the cutter inserts.
Incidentally, in order to reduce the cost of processing workpieces, there is a tendency in the operation of machine tools to perform a heavy-duty processing at a high feed rate with rotary cutters having cutter inserts of small sizes, so that a reliable cutter having a high performance is required. To meet these requirements, it is essential to employ the support members which are not subject to wear or abrasion over a prolonged period of time. In this respect, since the support members in the rotary cutter mentioned above are made of cast steel, in the case of the heavy-duty processing, burrs or wear develop in the support members and the rotary cutter becomes low endurability.
We have, therefore, made an extended study over the improvement of the cutter of the above-mentioned type and tackled especially on whether it is possible to form the support members of a powdered sintered material, particularly of cemented carbide, cermet, ceramics or high speed steel by means of extrusion molding which is advantageous with regards to manufacturing cost.
However, it has been proved that when forming the support members by the molding, if the same depth as that of the recess of the conventional support member is given to the recess of the support member under consideration, a thickness thereof should be made unnecessarily large, so that it is impossible to impart compactness to the rotary cutter. That is to say, in the molding, if a work member to be constructed has a recess to be shaped, the thickness of the work member is to be preferably selected as more than three times a depth of the recess thereof, so that the member has to be unnecessarily thick.